Coating compositions containing reactive diluents and methods

ABSTRACT

The present invention provides coating compositions that include reactive diluents and have high performance, low VOC levels, and low irritation levels. Certain embodiments of the present invention include water and water-dispersible polymers and other embodiments do not include water.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] The present application claims the benefit of U.S. ProvisionalApplication No. 60/478,070, filed on Jun. 12, 2003, which isincorporated herein by reference in its entirety.

BACKGROUND

[0002] There is a significant need for lower VOC-containing (volatileorganic compound-containing) systems in the coatings industry due toincreasing environmental restrictions. Typically, lower VOC-containingsystems have been achieved by using lower molecular weight polymers.However, this can result in products having poorer performance.

[0003] In an effort to reduce the amount of VOC's released, and maintainperformance, manufacturers have been using water-based polyurethanes.Such water-based polyurethanes are usually linear polymers and producefilms that have chemical resistance lower than the highly crosslinkedfilms of solvent-borne urethane systems. Preparing the polyurethanecoating compositions by pre-crosslinking a water-based polyurethanepolymer can be accomplished by incorporating a large amount of monomersthat have more than two reactive functional groups in the prepolymerstage. However, this results in highly viscous prepolymer blends thatcannot be easily dispersed in water. Diluents have been used to addressthis problem of viscosity, but many are highly irritating either toskin, eyes, or both. In many instances the presence of an “irritating”diluent will require that extensive industrial hygiene measures beundertaken before using the product. However, such measures may not bepractical and such products may not be selected as a result.

[0004] Thus, what is needed are coating compositions that have highperformance, low VOC levels, and low irritation levels.

SUMMARY

[0005] The present invention provides coating compositions that includereactive diluents and have high performance, low VOC levels, and lowirritation levels. Certain embodiments of the present invention includewater and water-dispersible polymers and other embodiments do notinclude water.

[0006] Preferred water-dispersed coating compositions include no morethan seven weight percent (wt-%) (more preferably no more than 4 wt-%)volatile organic compounds (VOC). However, certain other compositions,e.g., alkyd-based compositions, may contain higher VOC levels.

[0007] In one embodiment, a coating composition is provided thatincludes: a water-dispersible polymer (e.g., polyurethanes, epoxies,polyamides, chlorinated polyolefins, acrylics, oil-modified polymers,polyesters, and mixtures or copolymers thereof); a reactive diluent thatincludes a compound having a molecular weight of at least 350 grams/mole(preferably a molecular weight of 350 grams/mole to 1000 grams/mole),wherein the reactive diluent is substantially free of ethylene oxide andpropylene oxide moieties and has an OH-functionality of no more than 30milliequivalents KOH/gram; and water.

[0008] In another embodiment, a coating composition is provided thatincludes a water-dispersible polymer, a substantially non-irritatingreactive diluent, and water. If the reactive diluent is provided as amixture of compounds, the mixture as a whole is substantiallynon-irritating. That is, the phrase “reactive diluent” can encompass oneor more compounds. If it is a mixture of compounds, the entire mixturemust be substantially nonirritating.

[0009] In another embodiment, a coating composition is provided thatincludes an oil-modified polymer (e.g., an alkyd, an oil-modifiedpolyurethane, oil-modified epoxy, oil-modified polyamide, oil-modifiedacrylics, and mixtures or copolymers thereof); and a reactive diluentthat includes a compound having a molecular weight of at least 350grams/mole (preferably a molecular weight of 350 grams/mole to 1000grams/mole), wherein the reactive diluent is substantially free ofethylene oxide and propylene oxide moieties and has an OH-functionalityof no more than 30 milliequivalents KOH/gram. The oil-modified polymeris water-dispersible for certain embodiments.

[0010] In another embodiment, a coating composition is provided thatincludes an oil-modified polymer and a substantially non-irritatingreactive diluent. If the reactive diluent is provided as a mixture ofcompounds, the entire mixture is substantially non-irritating.

[0011] Typically, the water-dispersible polymer includes amine or acidfunctionality. It can also include ethylenic unsaturation (e.g.,(meth)acrylate functionality or auto-oxidative carbon-carbon doublebonds).

[0012] The reactive diluent can include a (meth)acrylate (wherein“(meth)acrylate” refers to an acrylate and a methacrylate), a vinylether, a (meth)allyl ether (wherein (meth)allyl ether refers to an allylether and a methallyl ether), or mixtures or copolymers thereof.Preferably, the reactive diluent includes a (meth)acrylate-functionalcompound, such as those selected from the group consisting ofdi-(trimethyolpropane tetraacrylate), di-(trimethyolpropanetetramethacrylate), and mixtures thereof.

[0013] The present invention also provides methods for coating thatinvolve applying a coating composition to a substrate and allowing thecoating composition to harden. The present invention also providescoatings prepared or preparable from the coating compositions describedherein. For example, a coating of the present invention is preparable bya method that involves applying a coating composition of the presentinvention to a substrate and allowing the coating composition to harden.

[0014] The present invention also provides a method of preparing acoating composition, the method involves: providing a mixture thatincludes a water-dispersible polymer and a reactive diluent having aviscosity below 100,000 centipoise (cps) at processing or usetemperatures, wherein the reactive diluent has a molecular weight of atleast 350 grains/mole and is substantially free of ethylene oxide andpropylene oxide moieties and has an OH-functionality of no more than 30milliequivalents KOH/gram; and dispersing the mixture in water.Significantly, because of the use of the reactive diluent, this processdoes not require the need for added solvent.

[0015] As used herein, a “reactive diluent” includes one or morerelatively low molecular weight compounds that react with at least oneof the following: a polymer (e.g., a water-dispersible polymer such as apolyurethane), itself, another reactive diluent, or any combination ofthese; a reactive diluent can form an interpenetrating network with thepolymer or can crosslink with the polymer; and can be a monomer,oligomer, or polymer.

[0016] Also herein, “water-dispersible” means the polymer is itselfcapable of being dispersed into water (i.e., without requiring the useof a separate surfactant) or water can be added to the polymer to form astable dispersion (i.e., the dispersion should have at least one monthshelf stability at normal storage temperatures).

[0017] Also herein, “a,” “an,” “the,” “at least one,” and “one or more”are used interchangeably.

[0018] Also herein, the recitations of numerical ranges by endpointsinclude all numbers subsumed within that range (e.g., 1 to 5 includes 1,1.5, 2, 2.75, 3, 3.80, 4, 5, etc.).

[0019] Also herein, the terms “comprises” and variations thereof do nothave a limiting meaning where these terms appear in the description andclaims.

[0020] The above summary of the present invention is not intended todescribe each disclosed embodiment or every implementation of thepresent invention. The description that follows more particularlyexemplifies illustrative embodiments. In several places throughout theapplication, guidance is provided through lists of examples, whichexamples can be used in various combinations. In each instance, therecited list serves only as a representative group and should not beinterpreted as an exclusive list.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

[0021] Coating compositions of the present invention include a reactivediluent and either a water-dispersible polymer or an oil-modifiedpolymer, which can be water-dispersible or not. When combined with thepolymer, the reactive diluent is capable of providing a lowVOC-containing composition.

[0022] Preferably, coating compositions of the present invention have aviscosity below 100,000 cps, more preferably below 30,000 cps, even morepreferably below 15,000 cps, even more preferably below 5,000 cps, andmost preferably below 1,000 cps at processing or use conditions.

[0023] Preferably, the coating compositions include no more than 7weight percent (wt-%) volatile organic compounds. More preferably, thecoating compositions of the present invention include no more than 4wt-% volatile organic compounds. Volatile organic compounds are definedin U.S. Pat. No. 6,048,471 (Henry) and in the U.S. Federal Register:Jun. 16, 1995, volume 60, number 111.

[0024] Coating compositions of the present invention preferably includea reactive diluent in an amount of at least 5 weight percent (wt-%),more preferably at least 10 wt-%, and most preferably at least 15 wt-%,based on the combined weight of the reactive diluent and the polymercomponent of the composition. Coating compositions of the presentinvention preferably include a reactive diluent in an amount of no morethan 40 weight percent (wt-%), more preferably no more than 30 wt-%, andmost preferably no more than 25 wt-%, based on the combined weight ofthe reactive diluent and the polymer component of the composition.

[0025] Water-dispersed coating compositions of the present inventionpreferably include at least 40 wt-% water, based on the total weight ofthe composition. Water-dispersed coating compositions of the presentinvention preferably include no more than 80 wt-% water, and morepreferably no more than 70 wt-%, based on the total weight of thecomposition.

[0026] The coating compositions of the present invention may be appliedto a variety of substrates including wood, cement, tile, metal, plastic,glass, optical fibers, and fiberglass. Coating compositions can beapplied to a substrate by a variety of methods known to those skilled inthe art. Such methods include spraying, painting, rollcoating, brushing,fan coating, curtain coating, spreading, air knife coating, die-coating,vacuum coating, spin coating, electrodeposition, and dipping. Thethickness of the coatings will vary with the application. Typically, thecoatings will have a thickness of 0.1 to 20 mils (0.00025 to 0.0508centimeters (cm)), however, thicker or thinner coatings are alsocontemplated depending on, for example, the desired coating properties.

[0027] Compounds that function as reactive diluents are of relativelylow molecular weight and can be reactive monomers, oligomers, or lowmolecular weight polymers. A compound that can function as a reactivediluent is one that can react with at least one of the polymer (thewater-dispersible polymer or oil-modified polymer), itself, anotherreactive diluent, or all of these. The polymer and reactive diluent canform, for example, an interpenetrating network. Alternatively, thereactive diluent can participate in crosslinking the polymer.

[0028] Suitable reactive diluent compounds have a relatively lowmolecular weight. Preferably, suitable reactive diluent compounds have amolecular weight of at least 350 grams/mole (g/mol). Preferably, themolecular weight is no more than 1000 g/mol.

[0029] Preferred reactive diluents are also substantiallynon-irritating, more preferably essentially non-irritating, and mostpreferably completely non-irritating. If the reactive diluent isprovided as a mixture of compounds, the entire mixture is substantiallynon-irritating, preferably essentially non-irritating, and morepreferably completely non-irritating.

[0030] A “substantially non-irritating” diluent has a Draize rating ofno more than 1 for skin (on a scale of 0 to 8) and no more than 10 foreyes (on a scale of 0 to 110). An “essentially non-irritating” diluenthas a Draize rating of no more than 0.5 for skin and no more than 5 foreyes. A “completely non-irritating” diluent has a Draize rating of nomore than 0.1 for skin and no more than 3 for eyes.

[0031] Preferred reactive diluents are substantially free of ethyleneoxide and propylene oxide moieties. More preferably, they areessentially free of ethylene oxide and propylene oxide moieties. Mostpreferably, they are completely free of ethylene oxide and propyleneoxide moieties. “Substantially free” means that less than 5 wt-%ethylene oxide and propylene oxide moieties are present in the reactivediluent. “Essentially free” means that less than 1 wt-% ethylene oxideand propylene oxide moieties are present in the reactive diluent.“Completely free” means that less than 0.5 wt-% ethylene oxide andpropylene oxide moieties are present in the reactive diluent.

[0032] Preferred reactive diluents have an OH-functionality of no morethan 30 milliequivalents KOH/gram (meq/g). Preferably, the reactivediluent has an OH-functionality of no more than 25 meq/g. Morepreferably, the reactive diluent has an OH-functionality of no more than20 meq/g.

[0033] Reactive diluents typically include compounds with ethylenicunsaturation. Suitable such compounds include a (meth)acrylate, a vinylether, a (meth)allyl ether, or mixtures or copolymers thereof. Examplesof (meth)acrylate-functional reactive diluents includedi-(trimethyolpropane tetraacrylate), di-(trimethyolpropanetetramethacrylate), di(pentaerythritol hexaacrylate),di-(pentaerythritol hexamethacrylate), pentaerythritol tetraacrylate,and pentaerythritol tetramethacrylate. Examples of vinyl ether reactivediluents include di-(trimethyolpropane tetravinyl ether),di-(pentaerythritol hexavinyl ether), and pentaerythritol tetravinylether. Examples of (meth)allyl ether reactive diluents includedi-(trimethyolpropane tetraalyl ether), di-(trimethyolpropanetetramethallyl ether), di(pentaerythritol hexaallyl ether),di-(pentaerythritol hexamethallyl ether), pentaerythritol tetraallylether, and pentaerythritol tetramethallyl ether. Preferred reactivediluent compounds are (meth)acrylate functional, which include acrylatefunctionality and methacrylate functionality. Preferred reactivediluents include (meth)acrylate functional compounds. Of these, thepreferred reactive diluent compounds are di-(trimethyolpropanetetraacrylate) and di-(trimethyolpropane tetramethacrylate). Reactivediluents used in coating compositions of the present invention ifdesired can include mixtures of compounds.

[0034] Polymers suitable for the coating compositions of the presentinvention are either water-dispersible or oil-modified, which can bewater-dispersible if desired. Such polymers are well-known in thecoating industry and include a wide variety of polymers.

[0035] The polymers preferably include reactive functionalities that arecapable of reacting with the aforementioned reactive diluent(s). Onesuch preferred polymer includes ethylenic unsaturation and, when cured,provides a hard, durable coating. Such ethylenic unsaturation ispreferably in the form of (meth)acrylate or auto-oxidative carbon-carbondouble bonds.

[0036] Suitable water-dispersible polymers include polyurethanes,epoxies, polyamides, chlorinated polyolefins, acrylics, oil-modifiedpolymers, polyesters, and mixtures or copolymers thereof, for example.Such polymers are readily synthesized and made to be water dispersibleusing conventional techniques. For example, the incorporation of amineor acid functionality produces water dispersibility.

[0037] Oil-modified polymers can also be used if desired, whether waterdispersible or not. As used herein, oil-modified polymers are broadlydefined to include polymers that contain oils and/or oil basedderivatives such as glyceride oils (monoglycerides, diglycerides, andthe like), fatty acids, fatty amines, and mixtures thereof. Examples ofsuch oil-modified polymers include, alkyds, oil-modified polyurethanes,oil-modified epoxies, oil-modified polyamides, oil-modified acrylics,and mixtures or copolymers thereof. Preferably, the oil-modified polymeris an oil-modified polyurethane or an alkyd. Such polymers are readilysynthesized and can be made to be water dispersible if desired usingconventional techniques.

[0038] Water-dispersible polyurethanes are particularly preferred. Thesepolymers may be made in a variety of ways. One suitable method includesreacting one or more isocyanates with one or more hydroxy-functionalcompounds. Preferred such polymers include ethylenic unsaturation aswell as salt-forming functionality. The ethylenic unsaturation can beintroduced into a polyurethane, for example, by reacting theaforementioned isocyanate with a hydroxy-functional acrylate,methacrylate, allyl ether, vinyl ether, monoglyceride, diglyceride, anester polyol, or oil-modified polymers. The preferred oil-modifiedpolymer useful in preparing an ethylenic unsaturated water-dispersiblepolyurethane is an alkyd. Preferred ethylenically unsaturatedpolyurethanes include (meth)acrylate or auto-oxidative carbon-carbondouble bond functionality.

[0039] Suitable isocyanates include diisocyanates, triisocyanates, andother polyisocyanates. Preferred polyisocyanates for practicing theinvention are polyisocyanates having 4 to 25 carbon atoms and from 2 to4 isocyanate groups per molecule. Examples of isocyanates are thoseconventionally used in making polyurethanes, including aliphatic,cycloaliphatic, aromatic isocyanates, and mixtures thereof.

[0040] Suitable hydroxy-functional ethylenically unsaturated compoundsfor reaction with the isocyanate include hydroxy-functional(meth)acrylates. Examples of suitable hydroxy-functional (meth)acrylatesinclude alkyl and cycloalkyl hydroxy-functional (meth)acrylates, such as2-hydroxyethyl (meth)acrylates, 3-hydroxypropyl (meth)acrylates,4-hydroxybutyl (meth)acrylates, 2-hydroxy-2-methylethyl (meth)acrylates,and 4-hydroxycyclohexyl (meth)acrylates, as well as other similarhydroxy-functional aliphatic (meth)acrylates. Other suitablehydroxy-functional (meth)acrylates include hydroxy-functional(meth)acrylate polyesters such as caprolactone2-((meth)acryloyloxy)ethyl esters, dicaprolactone2-((meth)acryloyloxy)ethyl esters, and higher molecular weightcaprolactone homologues, and hydroxy-functional (meth)acrylatepolyethers.

[0041] Another type of hydroxy-functional ethylenically unsaturatedcompound for use in making polyurethanes is a hydroxy-functional(meth)allyl ether. Suitable hydroxy-functional (meth)allyl ethersinclude at least one hydroxyl group and one or more allyl ether groups,such as hydroxyethyl allyl ether, hydroxypropyl allyl ether,trimethylolpropane monoallyl ether, trimethylolpropane diallyl ether,trimethylolethane monoallyl ether, trimethylolpropane dimethallyl ether,and the like.

[0042] Vinyl ethers may also be utilized in making ethylenicallyunsaturated polyurethanes. A suitable vinyl ether compound includes atleast one hydroxyl group and one or more vinyl ether groups. Examples ofsuitable vinyl ethers include 4-hydroxybutyl vinyl ether,cyclohexanedimethanol monovinyl ether, ethylene glycol monovinyl ether,diethylene glycol monovinyl ether, and the like.

[0043] Ethylenic unsaturation can also be incorporated into apolyurethane via reaction with an ester polyol made by reaction of anaromatic or aliphatic polyol containing at least two hydroxyl groups permolecule with a fatty acid wherein a portion of the fatty acid containsauto-oxidative carbon-carbon double bonds. Suitable polyols includeethylene glycol, ethylene glycol, proplylene glycol, 1,3 propane diol,1,3 butylene glycol, 1,4 butane diol, Bisphenol A, trimethylol propane,trimethylol ethane, pentaerythritol, glycerin, neopentyl glycol, andcyclohexane dimethanol, and mixtures thereof. Suitable unsaturated fattyacids include linoleic, palmitoleic, linolenic, eleostearic,arachidonic, ricinoleic acids, 10,12-octadecadienoic acid, and mixturesthereof.

[0044] Polyurethanes containing ethylenic unsaturation can also bedeveloped by utilizing the reaction product formed viatransesterification of an oil, containing auto-oxidative carbon-carbondouble bonds, with an aromatic or aliphatic polyol containing at leasttwo hydroxyl groups per molecule. Suitable oils include linseed oil,soybean oil, safflower oil, tall oil, sunflower oil, dehydrated casteroil, castor oil, ricine oil, tung oil, sardine oil, olive oil,cottonseed oil and mixtures thereof. Suitable polyols include ethyleneglycol, proplylene glycol, 1,3 propane diol, 1,3 butylene glycol, 1,4butane diol, Bisphenol A, trimethylol propane, trimethylol ethane,pentaerythritol, glycerin, neopentyl glycol, and cyclohexane dimethanol,and mixtures thereof.

[0045] Oil-modified polymers, preferably, hydroxyl-functional alkyds canalso be used to develop ethylenic unsaturated polyurethanes. Alkyds canbe prepared by any method known in the art. An example of a method toprepare an alkyd includes the transesterification of an oil and polyolwith a further reaction with polybasic acids and optionally, furtherpolyols. In addition, polybasic acids and fatty acids can be reactedwith polyols in suitable proportions. The reaction of the polyols withpolybasic acids and fatty acids and/or oils can be catalyzed bytransesterification catalysts such as calcium naphthenate, lithiumneodecanoate, zinc acetate, tin oxide and the like. A color stabilizersuch as trisnonyl phenyl phosphite may also be added.

[0046] Suitable oils and/or fatty acids derived therefrom that areuseful in making an alkyd or other oil-modified polymer includecompounds such as, for example, linseed oil, safflower oil, tall oil,cotton seed oil, ground nut, wood oil, tung oil, ricine oil, sunfloweroil, soya oil, castor oil, dehydrated castor oil, coconut oil, sardineoil, olive oil, and the like. These oils and/or fatty acids can be usedalone or as a mixture of one or more of the oils and/or fatty acids.

[0047] Suitable polyols useful in making an alkyd include compounds suchas, for example, aliphatic, cycloaliphatic and/or araliphatic alcoholshaving 1 to 6, preferably 1 to 4, hydroxy groups attached to nonaromaticor aromatic carbon atoms, such as, for example, ethylene glycol,proplylene glycol, 1,3 propane diol, 1,3 butylene glycol, 1,4 butanediol, Bisphenol A, trimethylol propane, trimethylol ethane,pentaerythritol, glycerin, neopentyl glycol, and cyclohexane dimethanol.These compounds can be used alone or as a mixture of one or morepolyols.

[0048] Suitable polybasic acids useful in making an alkyd includecompounds such as, for example, aliphatic, cycloaliphatic saturated orunsaturated and/or aromatic polybasic carboxylic acids, such as, forexample, dicarboxylic, tricarboxylic, and tetracarboxylic acids.Polybasic acids are broadly defined to include anhydrides of thepolybasic acids such as, for example, maleic anhydride, phthalicanhydride, succinic anhydride, tetrahydrophthalic anhydride,hexahydrophthalic anhydride, trimellitic anhydride, or mixtures thereof.These compounds can be used alone or as a mixture of one or morepolybasic acids.

[0049] Alkyds can also be prepared by reacting polybasic acids with acompound containing an amine to provide an amide containing alkyd.Examples of suitable amines include ethylene diamine, diethylenetriamine, triethylene tetra amine, and melamine 1,2-diamino propane,1,3-diamino propane, and the like; or amino alcohols such as, forexample, 2-amino-propan-1-ol, 3-amino-propan-1-ol,dimethylisopropanolamine, 2-amino-2-methyl-1-propanol,dimethylethanolamine, and the like. These amide containing alkyds can bedesigned to be amine and/or hydroxy functional and subsequently could beuseful in making a water dispersible polyurethane polymer.

[0050] Conventionally, to facilitate manufacture, the polyurethaneprepolymer can be made in the presence of a solvent that is either leftin the dispersion, or removed as one of the last steps in production toprovide a low solvent or solvent-free product. Solvents that can beeasily removed, are usually volatile solvents, such as acetone or methylethyl ketone. In place of such solvents (or a portion of such solvents),however, one or more reactive diluents as described above are used.

[0051] Chain extenders can also be used in the preparation of urethanepolymers. Examples of chain extenders include an alkyl amino alcohol,cycloalkyl amino alcohol, heterocyclic amino alcohol, polyamine (e.g.,ethylene diamine, diethylene triamine, etc.), hydrazine, substitutedhydrazine, hydrazide, amide, water or mixtures thereof.

[0052] In general, for water dispersibility, acid salt forming groupscan be introduced into the polymer by a number of methods. For example,a water-dispersible polyurethane can be made by reacting a suitablecompound (e.g., a polyisocyanate) with a compound containing activehydrogen and active acid groups neutralized by a neutralizing base.Suitable compounds having active hydrogen and active acid groups includehydroxy and mercapto carboxylic acids, aminocarboxylic acids,aminohydroxy carboxylic acids, sulfonic acids, hydroxy sulfonic acids,and aminosulfonic acids. Suitable neutralizing bases include inorganicbases such as sodium hydroxide, potassium hydroxide, lithium hydroxide,ammonia, triethylamine, and dimethyl ethanol amine.

[0053] Alternatively, for water dispersibility, basic salt forminggroups can be introduced into the polymers by reacting a suitablecompound (e.g., a polyisocyanate) with a compound containing activehydrogen groups and active basic groups neutralized with an acid.Suitable compounds having active hydrogen groups and active basic groupsinclude aliphatic, cycloaliphatic and heterocyclic amino alcohols, diolsand triols, amines, diamines, triamines, tetramines, and amides.Suitable neutralizing acids include organic acids such as formic acidand acetic acid, and inorganic acids such as hydrochloric acid andsulfuric acid.

[0054] For example, urethanes can be made water-dispersible byincorporating amine or acid functionality. For example, water-basedanionically stabilized polyurethane polymers are prepared by reactingpolyols and dihydroxy carboxylic acid compounds with an excess ofdiisocyanate to provide a carboxylic acid functional prepolymer havingNCO terminal groups. The acid groups can be neutralized with tertiaryamines to provide salt groups. The neutralized prepolymer can be readilydispersed in water. Alternatively, the anionic stabilizing group of thewater-dispersible polyurethane polymers can be replaced with cationicstabilizing groups or non-ionic stabilizing groups, to facilitate waterdispersibility.

[0055] Suitable additives for use in coating compositions of the presentinvention are described in Koleske et al., Paint and Coatings Industry,April, 2003, pages 12-86.

[0056] Certain embodiments of the present invention, particularly thosewith (meth)acrylate functional groups in the polymers and/or reactivediluents of the coating compositions, include polymers that are curableby UV or visible light. These coating compositions typically include afree-radical initiator, particularly a photoinitiator that induces thecuring reaction upon exposure to light. The photoinitiator makes upabout 0.1-10 wt-% of the coating composition.

[0057] Among photoinitiators suitable for use in the present inventionwith resins having (meth)acrylate or allyl ether functional groups arealpha-cleavage type photoinitiators and hydrogen abstraction typephotoinitiators. The photoinitiator may include other agents such as acoinitiator or photoinitiator synergist that aid the photochemicalinitiation reaction. Suitable cleavage type photoinitiators includealpha, alpha-diethoxyacetophenone (DEAP), dimethoxyphenylacetophenone(commercially available under the trade designation IRGACURE 651 fromCiba Corp., Ardsley, N.Y.), hydroxycyclo-hexylphenylketone (commerciallyavailable under the trade designation IRGACURE 184 from Ciba Corp.),2-hydroxy-2-methyl-1-phenylpropan-1-one (commercially available underthe trade designation DAROCUR 1173 from Ciba Corp.), a 25:75 blend ofbis-(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentyl phosphine oxide and2-hydroxy-2-methyl-1-phenylpropan-1-one (commercially available underthe trade designation IRGACURE 1700 from Ciba Corp.), a 50:50 blend of2-hydroxy-2-methyl-1-phenylpropan-1-one and2,4,6-trimethylbenzoyl-diphenylphosphine oxide (TPO, commerciallyavailable under the trade designation DAROCUR 4265 from Ciba Corp.),phosphine oxide, 2,4,6-trimethyl benzoyl (commercially available underthe trade name IRGACURE 819 and IRGACURE 819DW from Ciba Corp.),2,4,6-trimethylbenzoyl-diphenylphosphine oxide (commercially availableunder the trade designation LUCIRIN from BASF Corp., Mount Olive, N.J.),and a mixture of 70% oligo2-hydroxy-2-methyl-4-(1-methylvinyl)phenylpropan-1-one and 30%2-hydroxy-2-methyl-1-phenylpropan-1-one) (commercially available underthe trade designation KIP 100 from Sartomer, Exton, Pa.). Suitablehydrogen abstraction-type photoinitiators include benzophenone,substituted benzophenones (such as that commercially available under thetrade designation ESCACURE TZT from Fratelli-Lamberti, sold by Sartomer,Exton, Pa.), and other diaryl ketones such as xanthones, thioxanthones,Michler's ketone, benzil, quinones, and substituted derivatives of allof the above. Preferred photoinitiators include DAROCUR 1173, KIP 100,benzophenone, and IRGACURE 184. A particularly preferred initiatormixture is commercially available under the trade designation IRGACURE500 from Ciba Corp., which is a mixture of IRGACURE 184 andbenzophenone, in a 1:1 ratio. This is a good example of a mixture of analpha-cleavage type photoinitiator and a hydrogen abstraction-typephotoinitiator. Other mixtures of photoinitiators may also be used inthe coating compositions of the present invention. Camphorquinone is oneexample of a suitable photoinitiator for curing a coating compositionwith visible light.

[0058] A coating composition of the present invention can also include acoinitiator or photoinitiator synergist. The coinitiators can betertiary aliphatic amines (such as methyl diethanol amine and triethanolamine), aromatic amines (such as amylparadimethylaminobenzoate,2-n-butoxyethyl-4-(dimethylamino) benzoate,2-(dimethylamino)ethylbenzoate, ethyl-4-(dimethylamino)benzoate, and2-ethylhexyl-4-(dimethylamino)benzoate, (meth)acrylated amines (such asthose commercially available under the trade designations EBECRYL 7100and UVECRYL P104 and P115, all from UCB RadCure Specialties, Smyrna,Ga.), and amino-functional acrylate or methacrylate resin or oligomerblends (such as those commercially available under the tradedesignations EBECRYL 3600 or EBECRYL 3703, both from UCB RadCureSpecialties). Combinations of the above categories of compounds may alsobe used.

[0059] Coating compositions having resins with vinyl ether functionalgroups can be cured by UV or visible light using cationic-generatingphotoinitiators. Examples of suitable cationic-generatingphotoinitiators include super acid-generating photoinitiators, such astriarylsulfonium salts. One useful triarylsulfonium salt is triphenylsulfonium hexafluorophosphate.

[0060] Many coating compositions that may be cured by UV or visiblelight may also be cured with an electron beam. Techniques and devicesfor curing a coating composition using an electron beam are known in theart. These techniques do not require a photoinitiator for electron beamcure of the coating.

[0061] Coating compositions having polymer resins with (meth)acrylateand/or allyl functional groups may also be thermally cured using asuitable initiator. The thermal initiator typically facilitates thecuring process by a free radical mechanism and typically includes aperoxide or azo compound. Peroxide compounds suitable for use asinitiators in the coating compositions of the present invention includet-butyl perbenzoate, t-amyl perbenzoate, cumene hydroperoxide, t-amylperoctoate, methyl ethyl ketone peroxide, benzoyl peroxide,cyclohexanone peroxide, 2,4-pentanedione peroxide, di-t-butyl peroxide,t-butyl hydroperoxide, and di-(2-ethylhexyl)-peroxydicarbonate. Suitableazo compounds which may be employed as an initiator in the presentcompositions include 2,2-azo bis-(2,4-dimethylpentane-nitrile), 2,2-azobis-(2-methylbutanenitrile), and 2,2-azo bis-(2-methylpropanenitrile).

[0062] For coating compositions having a mixture of (meth)acrylate,allyl ether, and vinyl ether functional groups, a combination of curingprocedures may be used. For example, a coating composition having aresin with both (meth)acrylate and vinyl ether functional groupstypically includes an alpha-cleavage type and/or hydrogen abstractiontype photoinitiator for the (meth)acrylate groups and acationic-generating photoinitiator for the vinyl ether groups.

[0063] Other methods for curing the coating compositions of theinvention can be used alone or in combination with methods describedhereinabove. Supplemental curing methods include heat cure, chemicalcure, anaerobic cure, moisture cure, oxidative cure, and the like. Eachmethod of cure requires a corresponding curing initiator or curingagent, which is included in the composition. For example: heat cure canbe induced by peroxides; metal drier packages can induce an oxidativecure; multifunctional amines (for example isophorone diamine) can effecta chemical crosslinking cure through Michael addition of amine groupsonto acrylate reactive unsaturated groups. If these additionalinitiators are present in the coating composition they typically make up0.1-12% by weight of the curable coating composition. Means foreffecting cures by such methods are known to those of skill in the artor can be determined using standard methods.

[0064] Certain coating compositions of the invention also can includemetal driers. Typical driers include, for example, cobalt, manganese,lead, zirconium, calcium, cerium, lanthanum, and neodymium salts orcombinations thereof. Metal driers can be used in combination withaccelerators for certain embodiments. For example, water-dispersiblepolyurethane-polyethylene compositions can also include compounds suchas, for example, 1,10-phenanthroline, bipyridine, and the like, whichfunction as accelerators in combination with the metal driers.

[0065] Certain coating compositions of the present invention may alsoinclude one or more of a group of ingredients that can be calledperformance enhancing additives. Typical performance enhancing additivesthat may be employed include surface active agents, pigments, colorants,dyes, surfactants, thickeners, heat stabilizers, leveling agents,anti-cratering agents, curing indicators, plasticizers, fillers,sedimentation inhibitors, ultraviolet-light absorbers, opticalbrighteners, and the like to modify properties.

[0066] Coating compositions may include a surface-active agent thatmodifies the interaction of the curable coating composition with thesubstrate, in particular, the agent can modify the ability of thecomposition to wet a substrate. Surface active agents may have otherproperties as well. For example, surface active agents may also includeleveling, defoaming, or flow agents, and the like. The surface activeagent affects qualities of the curable coating composition including howthe coating composition is handled, how it spreads across the surface ofthe substrate, and how it bonds to the substrate. The surface activeagent may make up 0-5% by weight of the curable coating composition.

[0067] Surface active agents suitable for use in coating compositionsare known to those of skill in the art or can be determined usingstandard methods. Exemplary surface active agents includepolydimethylsiloxane surface active agents (such as those commerciallyavailable under the trade designations SILWET L-760 and SILWET L-7622from OSI Specialties, South Charleston, W.Va., or BYK 306 fromByk-Chemie, Wallingford, Conn.) and fluorinated surface active agents(such as that commercially available as FLUORAD FC-430 from 3M Co., St.Paul, Minn.). The surface active agents may include a defoamer. Suitabledefoamers include polysiloxane defoamers (such as amethylalkylpolysiloxane like that commercially available under the tradedesignation BYK 077 or BYK 500 from Byk-Chemie) or polymeric defoamers(such as that commercially available under the trade designation BYK 051from Byk-Chemie).

[0068] For some applications, a coating that is opaque, colored,pigmented or has other visual characteristics is desired. Agents toprovide such properties can also be included in coating compositions ofthe present invention. Pigments for use with the present invention areknown in the art. Suitable pigments include titanium dioxide white,carbon black, lampblack, black iron oxide, red iron oxide, yellow ironoxide, brown iron oxide (a blend of red and yellow oxide with black),phthalocyanine green, phthalocyanine blue, organic reds (such asnaphthol red, quinacridone red and toulidine red), quinacridone magenta,quinacridone violet, DNA orange, and/or organic yellows (such as Hansayellow). The composition can also include a gloss control additive or anoptical brightener, such as that commercially available under the tradedesignation UVITEX OB from Ciba-Geigy.

[0069] In certain embodiments it is advantageous to include fillers orinert ingredients in the coating composition. Fillers and inertingredients include, for example, clay, glass beads, calcium carbonate,talc, silicas, organic fillers, and the like. Fillers extend, lower thecost of, alter the appearance of, or provide desirable characteristicsto the composition before and after curing. Suitable fillers are knownto those of skill in the art or can be determined using standardmethods. Fillers or inert ingredients can make up from 0.1-40% by weightof the coating composition.

[0070] The invention may also include other ingredients that modifyproperties of the curable coating composition as it is stored, handled,or applied, and at other or subsequent stages. Waxes, flatting agents,mar and abrasion additives, and other similar performance enhancingadditives may be employed in this invention as required in amountseffective to upgrade the performance of the cured coating and thecoating composition. Desirable performance characteristics of thecoating include chemical resistance, abrasion resistance, hardness,gloss, reflectivity, appearance, or combinations of thesecharacteristics, and other similar characteristics.

EXAMPLES

[0071] Objects and advantages of this invention are further illustratedby the following examples, but the particular materials and amountsthereof recited in these examples, as well as other conditions anddetails, should not be construed to unduly limit this invention.

[0072] The following abbreviations have been used herein:

[0073] DMPA—Dimethylolpropionic acid (GEO, Allentown, Pa.)

[0074] DiTMPTA—Di-trimethyloipropane tetraacrylate (Sartomer, Exton,Pa.)

[0075] 4-HBA—4-Hydroxy butylacrylate (Aldrich, Milwaukee, Wis.)

[0076] TMP—Trimethylol Propane (Aldrich)

[0077] DESMOPHEN S-105-110—Polyester diol (Bayer, Pittsburgh, Pa.)

[0078] TEA—Triethyl Amine (Aldrich)

[0079] DBTDL—Dibutyl Tin Dilaurate (Air Products, Allentown, Pa.)

Example 1 Preparation of (meth)acrylate Functional PolyurethaneDispersion (PUD) with DiTMPTA Reactive Diluent

[0080] A reactor was charged with 96.0 parts DiTMPTA, 48.0 parts 4-HBA,91.4 parts DESMOPHEN S-105-110 polyester diol, 29.3 parts DMPA, 9.6parts TMP, and 500 ppm of 2,6 di-tert-butyl-4-methylphenol. The reactionmixture was heated to 80° C. under an air sparge, where upon 250 ppmDBTDL was added and the reaction processed until the isocyanate levelwas below 9.2%. The urethane polymer was cooled to 65° C. and thenneutralized with 22.1 parts TEA. The urethane polymer viscosity at 65°C. was 6,000 centipoise (cps) as measured by a BrookfieldDV-I+Viscometer and a Number 31 spindle at 1.5 revolutions per minute(RPM).

[0081] At a process temperature of 65° C., the (meth)acrylate urethanepolymer formed above was then dispersed into 895.5 parts roomtemperature deionized water and subsequently chain extended with 51.1parts hydrazine (35% in water). The dispersion was then adjusted to 35%solids with deionized water.

[0082] The physical properties of the chain extended (meth)acrylatefunctional polyurethane dispersion were as follows (NVM %=nonvolatilematerial by weight): EXAMPLE 1 NVM %  35% % VOC 1.4% (TEA)

Example 2 UV Curable Coating Composition with DiTMPTA Containing(meth)acrylate Functional PUD

[0083] Under agitation to a stainless steel mixing vessel was added 85parts of the dispersion from Example 1, 0.85 part, IRGACURE 500 fromCiba, 8.05 parts deionized water, 5.00 parts DOWANOL DPM from DowChemical, 1.00 part SURFYNOL 104PA from Air Products, and 0.10 part BYK333 from BYK Chemie. A 3-mil thick (0.00762-cm) wet film was thenapplied to a Leneta Form 7B test chart and air dried for 15 minutesfollowed by force dry for 5 minutes at 65° C. The dried (meth)acrylatepolymer film was then cured by mercury ultraviolet lamps. Total UVexposure was 1000 millijoules per square centimeter (mj/cm²).

[0084] Performance properties are outlined below. Gloss is reported inaccordance with ASTM test specification, D-523. All other cured filmproperties are reported on a scale of 1-10, with 10 being no effect orbest. TEST RESULT Gloss 60 degree measurement 88-90 1 hour Exposure tomustard    9+ 1 hour exposure to 100 proof  9 vodka 100 MEK double rubs 9 180 degree flexibility 10 Fingernail mar 10

[0085] Gloss measurement was performed with a Micro-Gloss 60 from BYKGardner in accordance with ASTM test method D-523.

[0086] 1-Hour spot test exposure to 100 proof vodka and to mustard wereperformed in accordance with ASTM test method D-1308.

[0087] MEK double rub testing was performed in accordance with ASTM testmethod D-5402.

[0088] 180-Degree flexibility was performed by bending the test chart180 degrees around a ½ inch (1.27 cm) diameter rod and visually lookingfor film cracking.

[0089] Fingernail mar was performed by rubbing the back of thefingernail softly across the cured coating and looking for surface mar.

[0090] The complete disclosures of the patents, patent documents, andpublications cited herein are incorporated by reference in theirentirety as if each were individually incorporated. Variousmodifications and alterations to this invention will become apparent tothose skilled in the art without departing from the scope and spirit ofthis invention. It should be understood that this invention is notintended to be unduly limited by the illustrative embodiments andexamples set forth herein and that such examples and embodiments arepresented by way of example only with the scope of the inventionintended to be limited only by the claims set forth herein as follows.

What is claimed:
 1. A coating composition comprising: awater-dispersible polymer; a reactive diluent comprising a compoundhaving a molecular weight of at least 350 grams/mole, wherein thereactive diluent is substantially free of ethylene oxide and propyleneoxide moieties and has an OH-functionality of no more than 30milliequivalents KOH/gram; and water.
 2. The coating composition ofclaim 1 wherein the water-dispersible polymer is selected from the groupconsisting of polyurethanes, epoxies, polyamides, chlorinatedpolyolefins, acrylics, oil-modified polymers, polyesters, and mixturesor copolymers thereof.
 3. The coating composition of claim 2 wherein thewater-dispersible polymer is a water-dispersible polyurethane.
 4. Thecoating composition of claim 3 wherein the water-dispersiblepolyurethane comprises amine or acid functionality.
 5. The coatingcomposition of claim 3 wherein the water-dispersible polyurethanecomprises ethylenic unsaturation.
 6. The coating composition of claim 5wherein the ethylenic unsaturation comprises (meth)acrylatefunctionality.
 7. The coating composition of claim 5 wherein theethylenic unsaturation comprises auto-oxidative carbon-carbon doublebonds.
 8. The coating composition of claim 7 further comprising a metaldrier.
 9. The coating composition of claim 1 wherein the reactivediluent comprises a compound having a molecular weight of 350 grams/moleto 1000 grams/mole.
 10. The coating composition of claim 1 wherein thereactive diluent comprises a (meth)acrylate, a vinyl ether, a(meth)allyl ether, or mixtures or copolymers thereof.
 11. The coatingcomposition of claim 10 wherein the reactive diluent comprises a(meth)acrylate-functional compound.
 12. The coating composition of claim11 wherein the (meth)acrylate-functional compound is selected from thegroup consisting of di-(trimethyolpropane tetraacrylate),di-(trimethyolpropane tetramethacrylate), and combinations thereof. 13.The coating composition of claim 1 further comprising a free-radicalinitiator.
 14. The coating composition of claim 1 wherein the reactivediluent is present in an amount of 5 wt-% to 40 wt-%, based on the totalweight of the reactive diluent and the water-dispersible polymer. 15.The coating composition of claim 14 wherein the reactive diluent ispresent in an amount of 10 wt-% to 30 wt-%, based on the total weight ofthe reactive diluent and the water-dispersible polymer.
 16. The coatingcomposition of claim 1 comprising no more than 7 wt-% volatile organiccompounds.
 17. A coating composition comprising: a water-dispersiblepolymer; a substantially non-irritating reactive diluent; and water. 18.The coating composition of claim 17 wherein the reactive diluent ispresent in an amount of 5 wt-% to 40 wt-%, based on the total weight ofthe reactive diluent and the water-dispersible polymer.
 19. The coatingcomposition of claim 18 wherein the reactive diluent is present in anamount of 10 wt-% to 30 wt-%, based on the total weight of the reactivediluent and the water-dispersible polymer.
 20. The coating compositionof claim 17 comprising no more than 7 wt-% volatile organic compounds.21. The coating composition of claim 17 comprising a(meth)acrylate-functional water-dispersible polyurethane, a reactivediluent comprising a (meth)acrylate-functional compound, and water. 22.The coating composition of claim 21 wherein the(meth)acrylate-functional compound is selected from the group consistingof di-(trimethyolpropane tetraacrylate), di-(trimethyolpropanetetramethacrylate), and combinations thereof.
 23. The coatingcomposition of claim 17 comprising an oil-modified water-dispersiblepolyurethane, a reactive diluent comprising a (meth)acrylate-functionalcompound, and water.
 24. The coating composition of claim 23 wherein the(meth)acrylate-functional compound is selected from the group consistingof di-(trimethyolpropane tetraacrylate), di-(trimethyolpropanetetramethacrylate), and combinations thereof.
 25. The coatingcomposition of claim 23 further comprising a metal drier.
 26. A coatingcomposition comprising: an oil-modified polymer; and a reactive diluentcomprising a compound having a molecular weight of at least 350grams/mole, wherein the reactive diluent is substantially free ofethylene oxide and propylene oxide moieties and has an OH-functionalityof no more than 30 milliequivalents KOH/gram.
 27. The coatingcomposition of claim 26 wherein the reactive diluent comprises acompound having a molecular weight of 350 grams/mole to 1000 grams/mole.28. The coating composition of claim 26 wherein the oil-modified polymeris selected from the group consisting of an alkyd, an oil-modifiedpolyurethane, an oil-modified epoxy, an oil-modified polyamide, anoil-modified acrylic, and mixtures or copolymers thereof.
 29. Thecoating composition of claim 28 wherein the oil-modified polymer is anoil-modified polyurethane.
 30. The coating composition of claim 28wherein the oil-modified polymer is an alkyd.
 31. The coatingcomposition of claim 26 wherein the oil-modified polymer is anoil-modified water-dispersible polymer.
 32. The coating composition ofclaim 31 wherein the oil-modified water-dispersible polymer is anoil-modified water-dispersible polyurethane.
 33. The coating compositionof claim 31 wherein the oil-modified water-dispersible polymer is awater-dispersible alkyd.
 34. The coating composition of claim 26 whereinthe reactive diluent comprises a (meth)acrylate, a vinyl ether, a(meth)allyl ether, or mixtures or copolymers thereof.
 35. The coatingcomposition of claim 34 wherein the reactive diluent comprises a(meth)acrylate-functional compound.
 36. The coating composition of claim35 wherein the (meth)acrylate-functional compound is selected from thegroup consisting of di-(trimethyolpropane tetraacrylate),di-(trimethyolpropane tetramethacrylate), and combinations thereof. 37.The coating composition of claim 26 further comprising a metal drier.38. The coating composition of claim 26 wherein the reactive diluent ispresent in an amount of 5 wt-% to 40 wt-%, based on the total weight ofthe reactive diluent and the oil-modified polymer.
 39. The coatingcomposition of claim 38 wherein the reactive diluent is present in anamount of 10 wt-% to 30 wt-%, based on the total weight of the reactivediluent and the oil-modified polymer.
 40. The coating composition ofclaim 26 comprising no more than 7 wt-% volatile organic compounds. 41.A coating composition comprising: an oil-modified polymer; and asubstantially non-irritating reactive diluent.
 42. The coatingcomposition of claim 41 wherein the oil-modified polymer is anoil-modified polyurethane.
 43. The coating composition of claim 41wherein the oil-modified polymer is an alkyd.
 44. The coatingcomposition of claim 41 comprising no more than 7 wt-% volatile organiccompounds.
 45. The coating composition of claim 41 comprising anoil-modified polyurethane, and a reactive diluent comprising a(meth)acrylate-functional compound.
 46. The coating composition of claim45 wherein the (meth)acrylate-functional compound is selected from thegroup consisting of di-(trimethyolpropane tetraacrylate),di-(trimethyolpropane tetramethacrylate), and combinations thereof. 47.The coating composition of claim 41 comprising an alkyd, and a reactivediluent comprising a (meth)acrylate-functional compound.
 48. The coatingcomposition of claim 47 wherein the (meth)acrylate-functional compoundis selected from the group consisting of di-(trimethyolpropanetetraacrylate), di-(trimethyolpropane tetramethacrylate), andcombinations thereof.
 49. The coating composition of claim 41 furthercomprising a metal drier.
 50. A method of coating comprising applyingthe coating composition of claim 1 to a substrate and allowing thecoating composition to harden.
 51. A coating preparable by the method ofclaim
 50. 52. A method of coating comprising applying the coatingcomposition of claim 17 to a substrate and allowing the coatingcomposition to harden.
 53. A coating preparable by the method of claim52.
 54. A method of coating comprising applying the coating compositionof claim 26 to a substrate and allowing the coating composition toharden.
 55. A coating preparable by the method of claim
 54. 56. A methodof coating comprising applying the coating composition of claim 41 to asubstrate and allowing the coating composition to harden.
 57. A coatingpreparable by the method of claim
 56. 58. A method of preparing acoating composition, the method comprising: providing a mixturecomprising a water-dispersible polymer and a reactive diluent, whereinthe mixture has a viscosity below 100,000 centipoise at processing oruse temperatures, and further wherein the reactive diluent includes acompound having a molecular weight of at least 350 grams/mole and issubstantially free of ethylene oxide and propylene oxide moieties andhas an OH-functionality of no more than 30 milliequivalents KOH/gram;and dispersing the mixture in water.